Device for lifting work pieces and work piece supports from a conveyor belt

ABSTRACT

A device for lifting work pieces and work piece supports from a conveyor belt and for supporting against operating pressure includes a base, a lift table and a slide disposed therebetween. The slide is movable by means of an adjustment drive between a first end position and a second end position. At least one of the parts is provided with lift faces which are formed by a peripheral segment of a cylinder element. Counter faces which cooperate with the lift faces are formed by rotatably mounted lift rollers which in the operating position of the lift table are released from pressure by supporting faces provided on the base, the lift table and the slide. This device is characterized by short adjustment paths of the slide, low friction faces and also by the end positions of the slide which should not be exactly defined and maintained.

BACKGROUND OF THE INVENTION

The invention relates to a device for lifting work pieces or work piecesupports from a conveyor belt. In a known device of this type supportfaces are formed on a slide, where the counter faces are formed on alift table. The counter faces are flat wedge surfaces, by means of whichthe lift table supports on the slide and thereby on the foundation. Theknown arrangement is disadvantageous in that the slide must travel arelatively large path for obtaining a certain lift, or additional meansmust be provided in the two end positions of the slide for arresting theslide. Moreover, the forces for moving the slide are relatively largedue to the sliding friction. Furthermore, the lift faces and the counterfaces are subjected to severe stress because the operating pressure istransmitted by these faces.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved liftingdevice for lifting work pieces from a belt conveyor. The inventivedevice is advantageous because of a favorable relationship of the liftto the adjustment movement of the slide, whereby only a rolling frictionis generated, so that also a lower drive output for the slide isrequired. The lift rollers are relieved from the support pressure in theoperating position of the lift table and the two end positions of theslide do not have to be exactly defined, so that special means areeliminated.

A particularly friction poor drive is obtained if the support faces aredesigned so that during the movement of the slide into the second endposition the lift table is at first lifted beyond its operating positionand can then be lowered to the support faces of the slide which in themeantime have moved below the support faces of the lift table.

For forming the support faces it is suggested to use cylinder elementswhich preferably are connected with the supporting parts of thosecylinders. A prelift element of a smaller diameter may be provided in anadvantageous manner in front of the cylinder elements at the faceopposite to the counter face. The cylinder elements may be made frominexpensive and very accurately-sized parts without an additionaltreatment of the support faces and may be mounted in a simple manner onthe supporting part. The prelift element facilitates the start of thelifting and may also be used for generating a defined prelift, if such aprelift is desired in one of the structural parts.

It is particularly advantageous if the support faces are providedbetween the slide and the lift table as well as between the slide andthe foundation. In this case the slide also performs a lift movementwhich adds to the relative lift movement of the lift table with respectto the slide. Thus, the lifting of the support faces or the adjustmentpath of the slide can be correspondingly reduced.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a plan view of a work station on a conveyor belt; and

FIGS. 2 and 4 illustrate a side view of the inventive device, partiallyin a section, in three different positions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A conveyor 10 has two conveyor belts 12 and 14 on which work piecesupports 16 are mounted and are taken along by means of frictioncontact. An abutment 20 is provided for stopping the work piece supports16 at a work station 18 which is introduceable into the path of movementof the work piece supports 16. Furthermore, a lift device 22 inaccordance with the invention is provided on the work station 18 betweenthe conveyor belts 12, 14. This device 22 is used to lift off the workpiece supports 16, which are arrested by abutment 20, from conveyorbelts 12, 14 and for supporting the supports 16 against the pressureexerted on the work pieces.

The lift device 22 has a foundation or stationary base 24, a lift table30 which is perpendicularly and displaceably guided in the foundation 24by means of bolts 26, 28, and a slide 32 which is provided therebetweenand is connected with a compressed air actuated adjustment drive 34. Twosupport bars 36 are provided on foundation 24. Bars 36 areperpendicularly extended in the plane of the drawing and are provided ontheir upper faces with supporting faces 38. Above the support bars 36,the lift table 30 is provided with two support bars 40 which havesupport faces 42 and project normally to the lift table. Furthermore,rotary lift rollers 44 are provided on foundation 24 and rotary liftrollers 46 are provided on the lift table table 30. Rollers 46 arepositioned above the lift rollers 44 of the foundation 24. The liftrollers 44, 46 are so dimensioned and disposed with respect to supportfaces 38, 42 that the respective opposing lift rollers 44, 46 do notengage with each other in the fully lowered position of the lift table30, illustrated in FIG. 2, whereby the opposing support faces 38, 42engage with each other.

The slide 32 has two support bars 48 extending vertically with respectto the plane of the drawing. Bars 48 have support faces 50 (FIG. 3)which are disposed on the upper and lower ends thereof. Furthermore, twocylinder elements 52 are mounted in each lift roller plane on slide 32.The distance between the cylinder elements as measured in the slidingdirection corresponds to the distance between the pair of lift rollers44,44 and 46,46. In contrast thereto, the relation of the cylinderelements 52 with respect to the support bars 48 of slide 32 deviatesfrom the relation of the lift rollers with respect to the support barson foundation 24 and lift table 30 by the dimension (FIG. 4), which isdescribed in more detail herein below.

A prelift element 54 is mounted on slide 32 in front of each cylinderelement 52. Each prelift element is formed by a bolt having asubstantially smaller diameter and a chamfered face which engages on thecircumference of the adjacent cylinder element 52. Each pair of partsformed of the cylinder elements 52 and the prelift element 54 representsone lift element having an additional support face 56 facing thefoundation 24 and an additional support face 58 facing the lift table 30(FIG. 3). The counter faces which are cooperating with the additionalsupport faces 56,58 are peripheral faces 60 and 62 of lift rollers 44and 46, respectively.

The adjustment drive 34 acts by means of a piston rod 64 on a roller 66which is rotatably mounted in a fork head 68 of slide 32. Inwardlydirected bars 70 are mounted on the free ends of the fork head by meansof which the piston rod 64 returns the slide 32 back into its initialposition, illustrated in FIG. 2, during the return stroke of the drive.The described device operates as follows:

In the initial position of the device illustrated in FIG. 2 the lifttable 30 with its support faces 42 lies on the support faces 38 of thefoundation 24. In this position the operating face of the lift table 30is disposed far below the plane of the conveyor belts, which in FIG. 2is indicated by the dash-dotted line 72. In this position the liftrollers are relieved from the weight of the lift table 30 and the slide32 is lowered to a position in which the prelift element 54 engages onthe lift rollers 44 of foundation 24. In this position the slide 32 maybe additionally supported on shoulders, not shown in the drawing, offoundation 24.

The slide 32 is displaced to the left by the adjustment drive 34 forlifting the lift table 30 into the operating position illustrated inFIG. 4, whereby a locked work piece support 16 above the device islifted by the conveyor belts 12,14. Thereby, the prelift elements 54 ofslide 32 penetrate into the wedge slot between the lift rollers 44 and46 and push the lift table 30 upwardly, whereby slide 32 also movesupwardly by the half of the traveled stroke. Simultaneously, the supportbars 48 of slide 32 approach the support bars 36 and 40 of foundation 24and lift table 30. The parts are so dimensioned and so chamfered thatthe support bars 48 of slide 32 can pass unhindered between the supportbars to the foundation and the lift table.

During the further process of the displacement movement the lift facesegments 56,58 formed on cylinder elements 52 abut on the lift rollers44,46 and further lift the lift table 30 until the same has reached itshighest position illustrated in FIG. 3, which is still above itsoperating position. In this position slide 32 is still removed from itsleft end position by the distance a (FIG. 4). Due to the overlifting oflift table 30 slots are formed between the support faces 38,42 and 50,so that slide 32 can at first be moved without a sliding frictionbetween the parts.

During the further movement of slide 32 the lift rollers 44,46 roll offon the rear peripheral faces of the cylinder elements 52, whereby slide32 and lift table 30 move downwardly. When slide 32 is moved from theposition in accordance with FIG. 3 further to the left by the distance ait has reached its second end position illustrated in FIG. 4, whereinthe support faces 38,42,50 of the parts engage with each other and theoperating face of the lift table 30 has its predescribed height. Thetolerances are so dimensioned that in the position in accordance withFIG. 4 the support is performed definitely over the support faces andthe lift rollers 44,46 are relieved from the support pressure oroperating pressure. This requires that the parts are already inengagement with each other on the support faces for a residual strokeand that the sliding friction between the slide 32 has to be overcome,on the one hand, and the foundation 24 and lift table 30, on the otherhand. During resetting the work piece support 16 on the conveyor belts12,14 the processes run in a reverse sequence.

Advantageously, means for centering and fixing of the work pieces orwork piece supports are provided on the lift table 30 which, however, donot belong to the invention and are therefore not illustrated in thedrawing.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofdevices for lifting workpieces and workpiece supports from a conveyorbelt differing from the types described above.

While the invention has been illustrated and described as embodied in adevice for lifting workpieces and workpiece supports from a conveyorbelt, it is not intended to be limited to the details shown, sincevarious modifications and structural changes may be made withoutdeparting in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims:
 1. A device for lifting work pieces orwork piece supports from a conveyor belt, comprising a stationary base;a lift table; and a movable slide disposed between said base and saidtable, said base, said lift table and said slide each having supportfaces; said slide also having additional support faces; a motor drivenadjustment drive connected to said slide to move the latter from a firstend position to a second end position so as to lift the lift table overthe additional support faces of the slide from a first non-operative endposition to a second operative end position, wherein the support faceson said lift table, said slide and said base engage with each other andtransmit pressure exerted on said table by work pieces to the base, saidtable and said base including rotatable lifting rollers (44,46) havingcounter faces (60, 62) which cooperate with the additional support faces(56, 58) formed on said slide, the support faces of said lift table andsaid slide (42, 50) being displaceable with respect to the additionalsupport faces and the counter faces being relieved from said pressure ina second end position of said slide (32).
 2. Device in accordance withclaim 1, wherein the additional support faces (56,58) are so formed thatthe lift table (30) is at first lifted during a movement of said slide(32) to said second operative end position of said lift table (30) to anintermediate position which is above said second operative position andthereafter is lowered so that the support faces (50) of said slide (32)are positioned below the support faces (42) of said lift table andengage the latter.
 3. Device in accordance with claim 2, whereincylinder elements (52) are fixedly connected to said slide (32), saidadditional support faces (56,58) being formed on circumferences of thecylinder elements (52).
 4. Device in accordance with claim 3, wherein aprelift element (54) is mounted next to each cylinder element (52) sothat each prelift element forms with an assigned cylinder element arespective additional support face.
 5. Device in accordance with claim4, wherein each prelift element (54) is a stationary bolt provided witha face opposite to the respective cylinder element (52) and having achamfered face which engages on said cylinder element.
 6. Device inaccordance with claim 4, wherein the additional support faces (56) onthe slide, which face the lift table (30) cooperate with the counterfaces (62) formed on the rollers (46) provided on the lift table.